DE60020070T2

DE60020070T2 - CATALYTIC HATCH FILTER WITH POROUS WALLS

Info

Publication number: DE60020070T2
Application number: DE60020070T
Authority: DE
Inventors: Robert James Duxford Brisley; Martyn Vincent Caxton Twigg; Anthony John Joseph Saffron Walden Wilkins
Original assignee: Johnson Matthey PLC
Current assignee: Johnson Matthey PLC
Priority date: 1999-08-13
Filing date: 2000-08-14
Publication date: 2006-01-19
Anticipated expiration: 2020-08-15
Also published as: DE60020070D1; EP1133355A1; AT295226T; US20040175315A1; EP1133355B1; JP2005500147A; US7097817B2; GB9919013D0; JP4782335B2; WO2001012320A1; US6753294B1

Description

These The invention relates to an exhaust system for an internal combustion engine, comprising a wall-flow filter, and in particular an exhaust system, wherein the wall-flow filter a Catalyst comprises.
exhaust from an internal combustion engine contain a large number of components, which are associated with the damage to health and the Environment. One of these is the component soot. A way of controlling the Amount of soot in the Exhaust gas is to use a filter downstream from the exhaust manifold or Exhaust manifold or exhaust transition piece, wherein it's the concept, soot, which is deposited on the filter to burn (oxidize), to thereby regenerate the filter.
One known type of soot filter is the wall flow filter. This filter may e.g. getting produced from a ceramic monolith, the channels in a honeycomb arrangement includes. A typical embodiment is shaped so that each channel is at one end or the other it is closed or blocked, and on the opposite End of the laterally and vertically adjacent channels. If you take them from one considered the two end, take the mutually closed and open ends of the channels the appearance of a chessboard. The ceramic material, from The filter can be made, has a pore size, the is sufficient to gas permeability or permeability to enable so that the pressure loss or pressure drop through the filter is relatively low, but prevents the passage of soot. In this way, soot is out the exhaust gases filtered.
The EP 0 341 832 A and the corresponding one US 4,902,487 A. describe a method and treatment system for soot-containing exhaust gas, wherein the gas also contains nitrogen oxide (NO), the method comprising passing the gas unfiltered over an oxidation catalyst to convert NO to nitrogen dioxide (NO 2 ), collecting the soot on a Filter downstream and burning the collected soot continuously at below 400 ° C by reaction with the NO 2 ; and there have been recent proposals to add further steps to the process and system, eg, stages for removal of nitrogen oxides (NO x ) (s. EP 0 758 713 A ). The EP 0 341 832 A and US 4,902,487 A. describe the Continuously Regenerating Trap ( CRT® (Continuous Regenerative Separator)) technology of Johnson Matthey and incorporated herein by reference.
In the procedure, which in the EP 0 341 832 A 10, the oxidation stage and the stage of filter combustion are carried out in two different honeycomb arrangements, each in a separate casing or jug or canister, or mounted within a single can or a single canister. However, there are difficulties in using both embodiments. A difficulty in the former embodiment is that there is limited space below a vehicle to mount each shroud or can or canister. In the last-mentioned embodiment, it is a problem that the construction or the construction of the jug or the canister is complicated. As further downstream processing steps are needed, these problems are exacerbated.
We have now found that these and other problems or difficulties can be overcome or reduced by performing each of the treatment steps on a single wall-flow filter or individual "brick" or "brick". The US 5 089 237 A discloses a soot combustion filter for an exhaust system of an internal combustion engine, the filter including a porous ceramic honeycomb block having channels mutually closed or plugged at the ends to define a flow path through the partitions of the channels Inlet end have a catalytic coating. We conclude from this document that the filter is used in a batch process in which soot is allowed to accumulate or accumulate on the filter and periodically burned off by raising the temperature and ensuring that sufficient oxygen (O 2 ) is available. Because of the combustion of a considerable amount of soot in a relatively small space, temperatures sufficiently high enough to exert destructive effects or effects on the filter are readily achieved. To limit such effect or effect, the filter provides the US 5 089 237 A provide a gas tight region in the baffles at the downstream end of the upstream channels. Although it is stated that the catalytic coating lowers the temperature at which soot combustion occurs, it is apparent that it does not make the gas-tight region unnecessary.
In one aspect, the invention provides an exhaust device for an internal combustion engine, the device comprising a wall-flow filter, the filter comprising a honeycomb arrangement defining a plurality of first channels plugged at an upstream end and a plurality of second ones Channels that are not clogged at the upstream end but clogged at the downstream end; an oxidation catalyst for the oxidation of NO in an Ab gas to NO 2 , wherein the oxidation catalyst is disposed on a substantially gas-impermeable zone at an upstream end of the second channels, a gas-permeable filter zone downstream of the oxidation catalyst for separating soot and a NO x absorber downstream of the filter zone, wherein the NO x absorber is disposed on a substantially gas-impermeable zone on the first channels, wherein soot filtered from the exhaust gas is continuously burned in NO 2 at up to 400 ° C.
The term "continuous" means that collected soot is burned in a continuous exhaust stream or flow; it thus excludes combustion of a large amount of collected or accumulated soot (except in the case of malfunction). However, it includes relatively small variations in the value or concentration of collected carbon black and in the gas composition in response to normal changes in engine operating conditions and a short term injection of reductants or NO x specific reactants to remove NO x downstream of the filter ,
Around misunderstandings to oppose or avoid, we mean in this description with "absorb" a significant or relevant Species on a governing or relevant surface from a body absorb or retain (otherwise "adsorb") and / or a species below the surface from a body, i.e. within the body, to take or retain.
Exhaust gases from an internal combustion engine also contain an unburned hydrocarbon (HC), carbon dioxide (CO 2 ), carbon monoxide (CO), steam (H 2 O (g)) and nitrogen (N 2 ). Their levels of NO x include NO and NO 2 , with the majority being NO. At least enough NO x should be present to provide at least enough NO 2 after the catalytic oxidation of NO to NO 2 to oxidize the collected soot as it is formed, or after a small accumulation or accumulation of soot. As in the above EP 0 341 832 A and described in WO 00 74 823 A, additional NO x may be supplied or delivered by, for example, injecting nitric acid or the product of local oxidation of ammonia (NH 3 ) or an ammonia precursor, such as urea.
The filter for use in the exhaust device of the present invention provides a gaseous flow path defined in part by the open ends of each channel that is occluded or plugged at the downstream end and the pores of the gas permeable wall of the channel. Soot in the gaseous exhaust gas enters the channel, but can not penetrate or pass through the pores of the channel wall. In this way, soot from the gaseous exhaust gas is filtered through the pores of the filter. In addition, the gaseous exhaust gas is forced to flow over the entire zone carrying the oxidation catalyst since the wall of the filter on which it is carried is substantially gas impermeable. This allows the best possible yield of NO 2 from NO at a given temperature and also avoids caking of the catalyst in the carbon black.
Preferably is the arrangement of channels, at the upstream and downstream ends The filter is plugged or plugged so that each channel the filter is closed at one or the other end thereof is clogged and on the opposite End of laterally and vertically adjacent channels, although other configurations or designs can be used. For example in one Arrangement of striped appearance are first longitudinal arrangements or longitudinal fields or longitudinal rows closed or plugged at one end, and the longitudinal rows or longitudinal arrangements of channels on both sides of the first arrangements are at the opposite Ends of the filter are closed or clogged, and so on. The Providing a filter that did not clog at least some or not sealed channels includes, thereby act as a bypass or bypass for the filter channels, is also within the scope of the present invention. The unclosed channels can also be used to introduce a reactant, the downstream is needed from the wall-flow filtration zone.
The channels are preferably square in cross-section, but can also be another Take shape, like a circular, rectangular, hexagonal or triangular.
Preferably, the oxidation catalyst, which advantageously is a compound including a platinum group metal (PGM), such as platinum (Pt) or palladium (Pd), which blocks filter pores in the gas, thereby blocking or blocking the zone or region substantially gas-impermeable close. Materials of the quality of a filter for making the filter suitably have a mean pore diameter in the range of 0.4 to 20 x 10 -3 inches (1 to 50 microns) for gas treatments at about atmospheric pressure, but other values may be more suitable for liquids or at higher or lower pressures. Although it is possible to make a filter in which the filter material itself is gas impermeable or the pore size is graded so that the upstream portion is clogged or closed However, gas permeability or permeability increases towards the filter zone, we prefer that the filter material be of uniform or similar pore size, and that zones carrying the catalyst be rendered gas impermeable by application or Application of materials on it. If the filter is ceramic, it may be a product of molding (eg, by extrusion or extruding or extrusion molding) and a composition containing sufficient volatile material to exit the required pores once removed, eg, by calcination. The filter, whether ceramic or metal, may be the product of a press or molding and sintering of a powder, possibly via a foam. While the filter material may be metal, we prefer that it be of a ceramic material such as cordierite, alumina, mullite, silicon carbide, zirconia or sodium / zirconia / phosphate. The honeycomb or honeycomb assembly typically has at least 50 cells per square inch ((cpsi) (7.75 cm -2 ), perhaps more, eg, up to 800 cpsi (124 cm -2 )). Generally, the range of 100 to 600 cpsi (15.5 to 93 cm -2 ) is preferred, of which 200 to 400 cpsi (31 to 62 cm -2 ) is most preferred.
The downstream passages of the filter include a NO x absorber (or NO x trap or trap) catalyst and, optionally, a NO x reduction catalytic converter or selective catalytic reduction (SCR) catalyst downstream of the NO x absorber one. The combination of the CRT® technology and the SCR of NO x with a nitrogen-containing compound such as NH 3 or urea is described in our WO 99 39 809. In another embodiment, the channels upstream of the oxidation catalyst may contain a sulfur oxide (SO x ) absorber (SOx -Abscheider or trap) form. The SO x absorber upstream may be included in embodiments with or without the NO x absorber or NO x reduction catalyst or SCR catalyst. As with the zone that includes the oxidation catalyst, in embodiments that include one or more of the SO x absorbers, NO x absorber, or NO x reduction catalyst or SCR catalyst, the zones of each catalyst or absorber are substantially gas impermeable and the gas impermeability is preferably provided by the catalyst or absorber or the catalyst carrier or absorber carrier.
The NO x absorber / precipitator comprises a compound including an alkali metal, an alkaline earth metal, rare earth metal or transition metal, or a mixed oxide capable of forming nitrates and / or nitrites of suitable stability under non-reducing conditions and for the development of Nitrogen oxides and / or nitrogen at reducing conditions, an oxidation catalyst, preferably Pt, and a reduction catalyst, preferably rhodium (Rh). Composite or composite oxides of, for example, an alkaline earth metal and copper may also be used, such as (using the letter codes of the Periodic Table) Ba-Cu-O or MnO 2 -BaCuO 2 , possibly with the addition of CeO 2 , or Y-Ba-Cu -O and Y-Sr-Co-O. The NO x reduction catalyst will typically include one or more PGM (s), but especially Pt, Pt / Rh, Pd / Rh or Pt / Pd / Rh. The SCR catalyst may be a copper-based material, Pt, a mixed oxide of vanadium (V 2 O 5 ) and titanium oxide (TiO 2 ), or a zeolite or mixtures of two or more thereof, and is preferably V 2 O 5 M / O 3 / TiO 2 . For further information, reference may be made to our WO 99 55 446 and WO 99 39 809. The SO x absorber may include an alkaline earth metal oxide or alkali metal oxide or mixtures of two or more thereof. Reference can be made to ours EP 0 814 242 A for more details.
In the exhaust apparatus wherein the filter comprises a NO x reduction catalyst or an SCR catalyst, the apparatus may include means for continuously injecting a reducing agent and / or NO x -specific reactant upstream or intermittently upstream of these catalysts. The oxidation catalyst of the invention may be present in two parts, optimized respectively for the oxidation of HC and CO or for the conversion of NO to NO 2 . In the embodiment involving both the NO x absorber and the reducing catalyst, they may be in different regions of the filter or combined, eg co-precipitated or co-precipitated or co-impregnated or co-impregnated or present as core composite layers or sandwich layers or as relatively fine (eg 1 to 500 μm) particles or superimposed in different primers or washcoats.
Preferably, the or each catalyst or absorber is supported or supported on a high surface area oxide support, preferably alumina (Al 2 O 3 ), TiO 2 or zirconia (ZrO 2 ) but the or each catalyst or absorber may be supported directly by the filter, ie without additional oxide carrier with a large surface.
Desirably, the catalyst (s) and, where present, the absorber, whether supported on a high surface area oxide or directly through the filter, increases the local or local pressure drop or pressure drop from the wall flow filter by one Factor of at least 2, and preferably up to 10. In one embodiment In this way, the filter zone itself can be catalyzed. A suitable catalyst is an oxidation catalyst to assist in the combustion of the carbon black, but more preferably, the catalyst includes a non-noble metal such as magnesium oxide (MgO), and most preferably the catalyst is a combination of lanthanum (La), cesium (Cs ) and vanadium pentoxide (V 2 O 5 ). Where the base metal is MgO, a preferred catalyst is Pt on MgO. If the surfaces of the pores of the filter zone are designed to support a catalyst, the pore diameter may be in the upper fifth of the above range or even higher, but such a coating should be thin enough to avoid the need for large pores that would structurally weaken the filter.
"Alkali metal" as defined herein excludes potassium (K), sodium (Na), lithium (Li), rubidium (Rb) or Cs; "Alkaline earth metal" includes barium (Ba), calcium (Ca), strontium (Sr) or magnesium (Mg); and "rare earth metal" includes cerium (Ce), La or Ytrrium (Y) or other lanthanides.
Of the Filter for use in the invention may be of any type appropriate way be packed. Packing materials that are commonly used close in the art a ceramic or steel wire net for wrapping and insulating the filter core; terminations or end plug to leak the exhaust gas through the wire mesh or to prevent grids or to support the mat; and Steel for the serving or jug or canister. A suitable binder can be used to the transition between the inlet and outlet tubes and the filter cross-section provide. openings for the Injection of additives or Additives or the introduction of sensor devices for On-board diagnostics or diagnostic facilities can also be provided where necessary.
Of the Filter for use in the present invention can be made are prepared by methods known in the art, such as exemplified by the illustration below. A method of manufacture a filter for use in the invention comprises a staged one Immersion in solutions and / or dispersions of precursors or precursor compounds the catalyst or absorber. In preferred embodiments this procedure closes that Processes the steps of coating a wall of a channel from a wall-flow monolith with at least one material, which is effective or effective to local or local gas permeability to humiliate the wall; and then applying to the coated Wall of at least one catalyst or absorber and optionally a calcination of the coated monolith.

(i) Anordnen einer Behältereinrichtung auf der Oberseite eines Wall-Flow-Monoliths, der eine Vielzahl von Kanälen in Wabenanordnung aufweist, wobei mindestens einige der Kanäle an dem Stromaufwärtsende verschlossen oder verstopft sind und mindestens einige der Kanäle, die an dem Stromaufwärtsende nicht verschlossen oder verstopft sind an dem Stromabwärtsende verschlossen sind; und dann
(ii) Zudosieren einer vorgegebenen Menge einer Flüssigkeit, die eine Grundierungs- oder Washcoat-Aufschlämmung ist, oder einer Lösung von einer Katalysator- oder Katalysatorvorläuferverbindung oder eines Gemischs von den zweien, in die Behältereinrichtung; oder umgekehrt und dann
(iii) durch Anlegen von Druck oder einem Vakuum, Abziehen der Flüssigkomponente in mindestens einen Teil der offenen Wall-Flow-Monolithkanäle, und ein Zurückhalten von im Wesentlichen der gesamten Menge innerhalb der Kanäle.

(i) placing a container means on top of a wall-flow monolith having a plurality of honeycomb channels, at least some of the channels being closed or plugged at the upstream end, and at least some of the channels not being closed at the upstream end clogged are closed at the downstream end; and then
(ii) metering a predetermined amount of a liquid, which is a primer or washcoat slurry, or a solution of a catalyst or catalyst precursor compound or a mixture of the two, into the container means; or vice versa and then
(iii) by applying pressure or a vacuum, withdrawing the liquid component into at least a portion of the open wall flow monolith channels, and retaining substantially all of the amount within the channels.

at a further embodiment the above procedure is applied to an unclosed one or unclogged monoliths, and the channels are closed or clogged after the coatings have been applied. If closing or clogging one end of a channel, includes the process involves the step of removing the coating on top of the end was applied before closing or plugging. at a further embodiment that concludes Process the coating only at the ends of the channels, which are predestined to be unclogged or unclogged to stay, i. the coating is not applied or applied on one end of a channel that is to be closed or clogged.
at a preferred embodiment the process includes the step of application or application a coating material for protection against aggressive media or Resist to a region or area where the application is or application of a primer or washcoat or a solution or Suspension of a catalyst or catalyst precursor or to delay a mixture thereof is. The coating composition (resist) may e.g. a wax or stearic acid.
Under In another aspect, the present invention provides a Internal combustion engine, which is an exhaust device according to the invention includes. Preferably, the internal combustion engine is a diesel engine.
Under In another aspect, the invention provides a vehicle, which is equipped with an internal combustion engine, preferably one Diesel engine including an exhaust device according to the invention.
In another aspect, the invention provides a method of treating soot-containing exhaust gas from an internal combustion engine, comprising the steps of first passing the soot-containing exhaust gas over an oxidation catalyst to convert NO in the exhaust gas to NO 2 , then filtering the gas, to deposit soot on a filter disposed in an exhaust system of the internal combustion engine, burning the soot deposited on the filter in NO 2 at up to 400 ° C, and then absorbing NO x from the exhaust gas in a NO x Absorber, wherein the filter is a wall-flow filter as defined above.
In order to The invention will be better understood, reference is made to the attached drawing, the one increased Cross-sectional view of an embodiment of a filter for Use in the present invention shows.
The 1 shows three adjacent channels 4 . 6 . 8th from a cordierite honeycomb filter 10 which has 200 cpsi (31 cm -2 ) and, before use, pores of about 10 μm in diameter. The channel 6 is clogged at the upstream end 12 of the filter 10 , and the other two channels 4 . 8th are each plugged or closed at the downstream end 14 of the filter 10 , This way, gas must enter the channel 6 enters at the upstream end, through the walls of the channel 6 flow or flow past the downstream end of the filter 10 to reach. Over a region or area or zone extending downstream from the opening to the channel 6 , the walls carry the coating 16 comprising an Al 2 O 3 primer or washcoat support and a metallic Pt oxidation catalyst. The coating 16 blocks or obstructs the pores of the filter walls. Over a region or region or zone that extends upstream from the outlet to the filter 10 , wear the channels 4 and 8th the coatings 18 . 20 bearing a NO x absorber composition including barium oxide (BaO) and a NO x reduction catalyst composition comprising Pt / Rh. To the coatings 18 . 20 The zone or area that will be covered with the coating will produce 20 coated, first covered with a coating (resist), such as a wax or stearic acid, during the application of the coating 18 , In this embodiment, the regions of the cordierite filter become 10 who the coatings 16 . 18 gas impermeable by the presence of the coating. Between the coatings 16 and 18 the walls of the channels remain 4 . 6 . 8th Gas permeable and provide a filtration zone 22 ready.
Diesel exhaust gas entering the reactor undergoes oxidation of HC, CO and NO in the presence of the coating 16 , Soot in the gas gets on the walls of the channels 4 . 6 . 8th at the filter zone or the filter area 22 and is burned by NO 2 , which originates from the oxidation of NO. The gas that contains the Rußverbrennungsprodukte passes or permeates through the wall of the filter and contacts the NOx -Abscheiderbeschichtung 18 that absorbs NO 2 . If sufficient NO 2 is stored or stored (as the nitrate, for example), which can be ensured by the vehicle's own diagnostic or diagnostic device of the vehicle, the coating can 18 can be regenerated with a rich or rich pulse of gaseous exhaust gas, ie gas that includes excess reducing agent, such as HC. The rich / lean operation or periodic rich / lean run can be controlled using the vehicle's engine management system. The obtained NO x -rich gas contacts the coating 20 including the NO x reduction catalyst, which causes the oxidation of HC and CO to reduce NO x in N 2 . In a further embodiment, wherein the coating 20 For example, if an SCR catalyst is an NO x -specific reactant, such as ammonia, may be injected at an upstream end of the filter at a rate and temperature that allows unreacted ammonia to enter the oxidation catalyst 16 escapes and the absorber 18 contacted, who regenerates it, and the catalyst 20 over which it reduces NO x to N 2 .
In order to a method of making the filter for use with the invention will be better understood, the following example is for the purpose of illustration provided.
The substrate is a cordierite honeycomb monolith of the quality of a filter of square cross-sectional channels 30 mm in diameter and 150 mm in length and has an average pore diameter of 10 μm, in which half of the passages of both ends of the monolith are plugged or closed, so that each channel of the monolith is closed or plugged at one or the other end and the opposite end of the laterally and vertically adjacent channels. One end of the monolith is characterized as an "inlet" and dipped 25 mm deep into an aqueous dispersion of hydrated Al 2 O 3 , then withdrawn, dried at 100 ° C, and then allowed to cool. The inlet end is then dipped to the same depth in an aqueous solution of 2% w / w (w / w) platinum chloride. The monolith is dried as before.
The unmarked end of the monolith is prepared by first dipping to a depth of 25 mm alternating with an aqueous solution of sodium stearate and then drying the resulting monolith at 100 ° C. The resulting monolith is then dipped in an aqueous hydrochloric acid and then water (two changes) to rinse off soluble components. The process produces an insoluble stearic acid layer as a coating (resist) which excludes any materials that are used in neutral or acidic solution. The coated with the coating composition monolith is then immersed to a depth of 50 mm in an aqueous solution of barium acetate and platinum chloride and dried. This dipping places these materials on an area upstream of the coated with the (resist) coated surface. Then, the coated monolith is immersed in 5% w / w aqueous sodium hydroxide to a depth of 25 mm to dissolve the stearic acid coating. This step is repeated twice, followed by two rinses with water. The coated monolith is then dried. The resulting monolith is then immersed to a depth of 25 mm in the Al 2 O 3 dispersion used at the inlet end and as described above. The coated monolith is then dried. Finally, it is immersed in a PURh solution to a depth of 25 mm. The coated monolith is then dried.
The resulting monolith is then calcined for one hour at 500 ° C to convert the metal salts to oxides or metals and to develop the surface of the Al 2 O 3 to provide a filter for use in the invention.

Claims

Exhaust device for an internal combustion engine, the device comprising a wall-flow filter ( 10 ), the filter comprising a honeycomb arrangement comprising a multiplicity of first channels ( 6 ) which are plugged at an upstream end ( 12 ) and a plurality of second channels ( 4 . 8th ), which are not clogged at the upstream end but are clogged at the downstream end (14), an oxidation catalyst ( 16 ) for oxidizing NO in an exhaust gas to NO 2 , wherein the oxidation catalyst is disposed on a substantially gas-impermeable zone at an upstream end of the second channels ( 4 . 8th ) is arranged, a gas-permeable filter zone ( 22 ) downstream of the oxidation catalyst for separating soot and a NO x absorber ( 18 ) downstream of the filter zone ( 22 ), wherein the NO x absorber at a substantially gas-impermeable zone on the first channels ( 6 ), wherein soot filtered from the exhaust gas is continuously burned in NO 2 at up to 400 ° C.
Exhaust device according to claim 1, wherein the arrangement the first and second channels so is that side and along adjacent channels are clogged at opposite ends.
Exhaust device according to claim 1 or 2, wherein the honeycomb arrangement further comprises a plurality of third channels, which are not clogged to a flow bypass to the first and second channels provide.
Exhaust device according to claim 1, 2 or 3, wherein the oxidation catalyst is a platinum group metal (PGM), preferably Pt and / or Pd.
An exhaust device according to any preceding claim, comprising a NO x reduction catalyst or a catalyst ( 20 ) for selective catalytic reduction (SCR) on a substantially gas impermeable zone on the first passages downstream of the NOx absorber.
Exhaust device according to claim 5, comprising means for injecting NO x specific reducing agent into the exhaust gas upstream of the SCR catalyst.
An exhaust device according to claim 5 or 6, wherein the SCR catalyst includes copper-based materials, Pt, a mixed oxide of vanadium and titanium, or a zeolite or mixtures of two or more thereof, and preferably represents V 2 O 5 / WO 3 / TiO 2 ,
An exhaust device according to claim 5, wherein the NO x reduction catalyst comprises one or more PGMs, preferably Pt, Pt / Rh, Pd / Rh, or Pt / Pd / Rh.
Exhaust device according upstream comprises any preceding claim, the means for injecting a reducing agent into the exhaust gas from the NO x absorbent.
Exhaust device according to any preceding claim, which additionally comprises an upstream SO x absorber on a substantially gas impermeable zone on the second channels of the oxidation catalyst.
Exhaust device according to any preceding claim, wherein the NO x absorber or the SO x absorber an alkaline earth metal oxide, an alkali metal oxide or a rare earth metal oxide or mixtures of any two or more thereof includes.
An exhaust device according to claim 11, wherein the alkali metal for potassium, Sodium, lithium, rubidium or cesium or a mixture of any two or more of them, the alkaline earth metal for barium, calcium, strontium or magnesium or a mixture of any two or more thereof, or the rare earth metal for Cerium, lanthanum or yttrium or another lanthanide or a mixture from any two or more of them.
Exhaust device according to any preceding claim, wherein the or each catalyst or absorber is supported on an oxide support greater Surface, preferably alumina, titania or zirconia becomes.
Exhaust device according to any preceding claim, wherein the catalyst or absorber or a carrier containing the catalyst or Absorber stops, the zone, including of the catalyst or absorber, substantially gas impermeable.
Exhaust device according to any preceding claim, the presence of any catalyst or absorber on a Wall-Flow-Filter the local pressure drop of the Wall-Flow-Filter a factor of at least 2, preferably at least 10, increased.
Internal combustion engine, preferably a diesel engine, the an exhaust device according to any includes the preceding claim.
Vehicle equipped with an internal combustion engine according to claim 16th
A method of treating soot-containing exhaust gas from an internal combustion engine, comprising the steps of first passing the soot-containing exhaust gas over an oxidation catalyst to convert NO in the exhaust gas to NO 2 , then filtering the gas to deposit soot on a filter that is in an exhaust system of the internal combustion engine is arranged, burning the soot deposited on the filter in NO 2 at up to 400 ° C and then absorbing NO x from the exhaust gas in a NO x absorber, wherein the filter is a wall-flow Filter ( 10 ) is as defined in claim 1.